A surface of a lotus leaf has a structure where nano-protrusions having a size of several hundreds of nanometers are disposed on a surface of a micro-protrusion having a size of −10 μm. The surface of the lotus leaf has super-hydrophobic and self-cleaning functions. Various methods for fabricating a super-hydrophobic surface by copying a micro-nano complex protrusion structure by a material having low surface energy are known. The super-hydrophobic surface has a merit of small contact angle hysteresis (a difference between an advancing contact angle and a receding contact angle). Accordingly, the super-hydrophobic surface is capable of being applied to various industry fields.
Among the known methods for fabricating the super-hydrophobic surface, there is a method for fabricating a super-hydrophobic surface on a wafer by using a micro-electromechanical system (MEMS). However, there are drawbacks in that the super-hydrophobic surface having an area that is larger than that of the wafer is not capable of being manufactured by the micro-electromechanical system and a manufacturing cost is very high.
Among methods proposed to overcome the drawbacks, there is a method for duplicating a micro-nano complex protrusion structure on a surface of a metal base material by (1) applying collision energy to the surface of the metal base material to form a micro-groove, (2) anodizing the metal base material to form nano-grooves in the micro-groove, and (3) applying a polymer material to the surface of the metal base material and then performing separation. This method has merits in that a size is not limited and the duplicated polymer material is flexible to be attachable to various three-dimensional articles.
However, in the aforementioned method, it takes a long time to perform anodizing and polymer duplication processes, and the super-hydrophobic surface is embodied by only the polymer material. Accordingly, surface strength is weak as compared to a metal surface. Further, the duplicated polymer material should be attached to the surface of the article for embodying the super-hydrophobic surface. Accordingly, it is difficult to apply the aforementioned method to the surface of a complicated and three-dimensional article.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.